On Tue, Sep 22, 2020 at 09:44:18AM -0700, Eric Biggers wrote: > From: Eric Biggers <ebiggers@xxxxxxxxxx> > > There's no need for mnt_want_write_file() to increment mnt_writers when > the file is already open for writing, provided that > mnt_drop_write_file() is changed to conditionally decrement it. > > We seem to have ended up in the current situation because > mnt_want_write_file() used to be paired with mnt_drop_write(), due to > mnt_drop_write_file() not having been added yet. So originally > mnt_want_write_file() had to always increment mnt_writers. > > But later mnt_drop_write_file() was added, and all callers of > mnt_want_write_file() were paired with it. This makes the compatibility > between mnt_want_write_file() and mnt_drop_write() no longer necessary. > > Therefore, make __mnt_want_write_file() and __mnt_drop_write_file() skip > incrementing mnt_writers on files already open for writing. This > removes the only caller of mnt_clone_write(), so remove that too. > > Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> > --- > > v3: added note to porting file. > v2: keep the check for emergency r/o remounts. > > Documentation/filesystems/porting.rst | 7 ++++ > fs/namespace.c | 53 ++++++++++----------------- > include/linux/mount.h | 1 - > 3 files changed, 27 insertions(+), 34 deletions(-) Ping.
